On this day in 1972, the Apollo 17 crew snapped this photograph, later dubbed "The Blue Marble." Photographed using a 70-millimeter Hasselblad camera with an 80-millimeter Zeiss lens, and credited to all three Apollo 17 astronauts (Eugene Cernan, Ronald Evans and Jack Schmitt), this rare image of a fully-illuminated Earth has become one of the world's most recognizable photographs. No human has since traveled far enough into space to see such a full view of earth, though similar shots have since been taken by unmanned spacecraft. [NASA History Office; image: Wikimedia]